Field of the Invention
Embodiments of the present invention relate to a camera module having a voice coil motor actuator and a method for auto-focusing thereof.
Discussion of the Related Art
Mobile terminals include highly integrated diverse functions and tend to be light in weight and have a small size. In addition, camera modules mounted in mobile terminals are downsizing including smaller lenses. Further, an optical system of a camera module requires an auto focus function to make an object clearly visible. Such an auto focus function needs various types of actuators to move a lens module to an optimal focal point. The auto focus of the camera module may also be varied in accordance with characteristics of the actuator for moving the lens module.
An auto focus actuator may include various types of actuators. Examples of various actuators include a voice coil motor (VCM) actuator, an actuator driven by a piezoelectric force and a MEMS actuator driven based on a capacitive method. In addition, the voice coil motor (VCM) actuator is configured of a magnetic circuit in which a permanent magnet is provided in a fixing unit of the camera module, with a coil attached to a lens module to drive, such that the voice coil motor actuator can drive the lens module, using Lorentz's force traveling through the coil.
Further, the voice coil motor actuator extracts a difference between magnetic flux values calculated from phase change of the lens module, using a sense attached to the lens module, only to calculate an optical value of auto focus for the lens module. In such voice coil motor actuator, three power supply sources have to be connected to the sensor to attach the sensor to the lens module. Accordingly, a manufacture process is complicated. In other words, at least five connectors have to be provided in the lens module of the voice coil motor actuator and the at least five connectors include two connectors for electrical connection with the coil located in the lens module and three connectors for electrical connection with the sensor located in the lens module. Accordingly, it is difficult to design and manufacture the voice coil motor actuator.
Moreover, in the voice coil motor actuator using the lens module having the sensor attached thereon, it takes quite a long time to move the lens module to an optimal position of auto focus. There may also be auto focus position errors in the lens module.